JP6793781B2 - Mirror with image display function for vehicles - Google Patents

Description

The present invention relates to a mirror with an image display function for a vehicle.

For example, Patent Document 1 describes a mirror with an image display function for a vehicle, which enables the mirror for a vehicle to display an image such as an image captured by an in-vehicle camera. In the mirror with an image display function for vehicles disclosed in Patent Document 1, a liquid crystal display device is provided inside the housing of the mirror for vehicles, and an image is displayed through a half mirror provided on the front surface of the mirror for vehicles. , Realizes image display with a mirror.

Japanese Unexamined Patent Publication No. 2014-201146 Japanese Unexamined Patent Publication No. 2011-45427

The half mirror has a visible light transmittance of about 30% to 70%, and there is a potential problem that the image with the half mirror is darker than the one without the half mirror. .. On the other hand, in Patent Document 2 which discloses a mirror with an information display function applied to mirrors for interior, cosmetics, crime prevention, and safety, a reflective polarizing plate is used as a half mirror to eliminate light loss. Is stated to be possible. However, when the present inventors constructed a mirror with an image display function using a reflective polarizing plate and used it in a vehicle, uneven brightness and uneven color (rainbow color, etc.) occurred in the mirror reflected image.
An object of the present invention is to provide a mirror with an image display function for a vehicle, which can display a bright image and can observe a mirror reflection image without unevenness.

The present inventors have diligently studied to solve the above problems, and found that the above unevenness of the mirror reflection image can be confirmed when observing the external landscape through the rear glass of the vehicle, and further studies based on this finding. The present invention was completed by repeating.

That is, the present invention provides the following [1] to [10].
[1] A mirror with an image display function for a vehicle, which includes a half mirror and an image display device, the half mirror includes an nλ / 4 retardation film and a reflective layer, and n is 1, 3, 5 or 7. In the mirror with an image display function, the nλ / 4 retardation film, the reflection layer, and the image display device are arranged in this order, and the reflection layer is a linear polarization reflection layer or a circular polarization reflection layer. , Mirror with image display function.
[2] The mirror with an image display function according to [1], wherein n is 1 or 3.
[3] The mirror with an image display function according to [1] or [2], wherein the reflective layer is a circularly polarized reflective layer.
[4] The mirror with an image display function according to [3], wherein the circularly polarized light reflecting layer includes a cholesteric liquid crystal layer.
[5] The mirror with an image display function according to [4], wherein the circularly polarized light reflecting layer includes three or more cholesteric liquid crystal layers.

[6] The method according to [4] or [5], wherein the half mirror includes the nλ / 4 retardation film, the circular polarization reflecting layer, and the 1/4 wave plate in this order. Mirror with image display function.
[7] The mirror with an image display function according to [6], wherein the circularly polarized light reflecting layer and the 1/4 wave plate are in direct contact with each other.
[8] With the image display function according to any one of [1] to [7], wherein the half mirror includes a front plate, and includes the front plate, the nλ / 4 retardation film, and the reflective layer in this order. mirror.
[9] The half mirror includes a front plate, the front plate is a laminated glass containing two glass plates and an intermediate layer between the two glass plates, and the intermediate layer is the nλ / 4 retardation film. The mirror with an image display function according to any one of [1] to [7] including.
[10] The half mirror is a laminated glass including two glass plates and an intermediate layer between the two glass plates, and the intermediate layer includes the nλ / 4 retardation film and the reflective layer [1]. ] To the mirror with an image display function according to any one of [7].

INDUSTRIAL APPLICABILITY The present invention provides a mirror with an image display function for a vehicle, which can display a bright image and can observe a mirror reflection image without unevenness. When the mirror with an image display function of the present invention is used as an inner mirror of a vehicle, the external landscape through the rear glass can be observed as a mirror reflection image without unevenness.

Hereinafter, the present invention will be described in detail.
In addition, in this specification, "~" is used in the meaning that the numerical values described before and after it are included as the lower limit value and the upper limit value. In the present specification, for example, angles such as "45 °", "parallel", "vertical" or "orthogonal" shall differ from the exact angles within a range of less than 5 degrees unless otherwise specified. Means. The difference from the exact angle is preferably less than 4 degrees, more preferably less than 3 degrees.
As used herein, "(meth) acrylate" is used to mean "one or both of acrylate and methacrylate".

In the present specification, the term "selective" for circularly polarized light means that the amount of light of either the right-handed circularly polarized light component or the left-handed circularly polarized light component is larger than that of the other circularly polarized light component. Specifically, when referring to "selective", the degree of circular polarization of light is preferably 0.3 or more, more preferably 0.6 or more, and even more preferably 0.8 or more. It is even more preferred that it is substantially 1.0.
Table In _{/ (I R + I L)} | Here, the degree of circular polarization, the intensity of the right circularly polarized light component of the light I _R, when the strength of the left-handed circularly polarized light component and I _L, | I _R -I _L Is the value to be.

In the present specification, the term "sense" for circularly polarized light means whether it is right-handed or left-handed. The sense of circularly polarized light is right-handed circularly polarized light when the tip of the electric field vector turns clockwise as time increases when viewed as the light travels toward you, and left when it turns counterclockwise. Defined as circularly polarized.

In the present specification, the term "sense" may be used for the twisting direction of the spiral of the cholesteric liquid crystal. Selective reflection by the cholesteric liquid crystal reflects the right circular polarization when the twist direction (sense) of the spiral of the cholesteric liquid crystal is right, transmits the left circular polarization, and reflects the left circular polarization when the sense is left, and right. Transmits circular polarization.

Visible light is light having a wavelength that can be seen by the human eye among electromagnetic waves, and indicates light in the wavelength range of 380 nm to 780 nm. Infrared light (infrared light) is an electromagnetic wave in a wavelength range longer than visible light and shorter than radio waves. Of the infrared rays, near-infrared light is an electromagnetic wave in the wavelength range of 780 nm to 2500 nm.

In the present specification, the term "image" of a mirror with an image display function means an image that can be visually observed from the front side when an image is displayed on the image display unit of the image display device. Further, in the present specification, the term "mirror reflection image" of a mirror with an image display function means an image that can be visually observed from the front side when an image is not displayed on the image display unit of the image display device. ..

In the present specification, the front phase difference is a value measured using AxoScan manufactured by Axometrix. In the present specification, the front phase difference may be referred to as Re. The measurement wavelength of the front phase difference is 550 nm unless otherwise specified. The front phase difference is a value measured by KOBRA 21ADH or WR (manufactured by Oji Measuring Instruments Co., Ltd.) in which light with a wavelength within the visible light wavelength range such as the center wavelength of selective reflection of the cholesteric liquid crystal layer is incident on the film normal direction. It can also be used. In selecting the measurement wavelength, the wavelength selection filter can be replaced manually, or the measured value can be converted by a program or the like for measurement.

In the present specification, the vehicle means a train, an automobile, or the like. As the vehicle, an automobile having a rear glass is particularly preferable.

<<< Mirror with image display function for vehicles >>>
A mirror with an image display function for a vehicle can be used as a rearview mirror (inner mirror) of a vehicle. The mirror with an image display function for a vehicle may have a frame, a housing, a support arm for attaching to the vehicle body, and the like for use as a rearview mirror. Alternatively, the mirror with an image display function for a vehicle may be molded for incorporation into a rearview mirror. In the mirror with an image display function for a vehicle having the above shape, the vertical and horizontal directions can be specified during normal use.

The mirror with an image display function for a vehicle may be in the form of a plate or a film, and may have a curved surface. The front surface of the mirror with an image display function for a vehicle may be flat or curved. It is also possible to make a wide mirror that can visually recognize the rear view and the like from a wide angle by bending the convex curved surface to the front side. Such a curved front surface can be manufactured by using a curved half mirror.
The curvature may be in the vertical direction, the horizontal direction, or the vertical direction and the horizontal direction. The curvature may have a radius of curvature of 500 to 3000 mm. More preferably, it is 1000 to 2500 mm. The radius of curvature is the radius of this circumscribed circle when the circumscribed circle of the curved portion is assumed in the cross section.

The mirror with an image display function of the present invention includes an image display device and a half mirror.
In the mirror with an image display function, an air layer may be present or an adhesive layer may be present between the image display device and the half mirror.
In the present specification, the surface on the half mirror side with respect to the image display device may be referred to as the front surface.
In the present specification, the "mirror with an image display function for a vehicle" may be simply referred to as a "mirror with an image display function".

<< Image display device >>
The image display device is not particularly limited. The image display device is preferably an image display device that emits (emits light) linearly polarized light to form an image, and more preferably a liquid crystal display device.
The liquid crystal display device may be a transmissive type or a reflective type, and is particularly preferably a transmissive type. The liquid crystal display device has IPS (In Plane Switching) mode, FFS (Fringe Field Switching) mode, VA (Vertical Alignment) mode, ECB (Electrically Controlled Birefringence) mode, STN (Super Twisted Nematic) mode, and TN (Twisted Nematic) mode. , OCB (Optically Compensated Bend) mode, or any other liquid crystal display device may be used. When the power of the image display device is turned off, the average visible light reflectance at a wavelength of 380 to 780 nm is preferably 30% or more, and more preferably 40% or more. This is to make the mirror with an image display function function as a mirror when the power is turned off. The reflection of visible light when the power of the image display device is turned off may be derived from the constituent members (reflection polarizing plate, backlight unit, etc.) of the image display device.
The visible light average reflectance means a numerical value calculated based on the visible light calculation method described in JIS A5759 by measuring the reflection spectrum with a spectrophotometer, and the spectrophotometer is, for example, JASCO Corporation. A spectrophotometer "V-670" manufactured by JASCO Corporation can be used.

The image shown in the image display unit of the image display device may be a still image, a moving image, or simply text information. Further, it may be a monocolor display such as black and white, a multicolor display, or a full color display. A preferable example of the image shown in the image display unit of the image display device is an image taken by an in-vehicle camera. This image is preferably moving.

The image display device may show, for example, the emission peak wavelength λR of red light, the emission peak wavelength λG of green light, and the emission peak wavelength λB of blue light in the emission spectrum at the time of white display. By having such an emission peak wavelength, a full-color image can be displayed. λR may have a wavelength in the range of 580 to 700 nm, preferably in the range of 61 to 680 nm. λG may have a wavelength in the range of 500 to 580, preferably in the range of 510 to 550 nm. λB may have a wavelength in the range of 400 to 500 nm, preferably in the range of 440 to 480 nm.

<< Half Mirror >>
The half mirror may be in the form of a plate or a film, and may have a curved surface. The half mirror may be flat or curved. The curved half mirror can be manufactured by using a curved front plate.
The half mirror includes a reflective layer and an nλ / 4 retardation film. It is preferable that the reflective layer and the nλ / 4 retardation film are laminated on each other in the same area of the main surface. In addition, in this specification, a "main surface" means the surface (front surface or back surface) of a plate-shaped or film-shaped member.

The half mirror may include other layers such as a faceplate or an adhesive layer. When the half mirror includes a front plate, the front plate, the nλ / 4 retardation film, and the reflective layer are preferably in this order. When the half mirror includes the front plate, the area of the main surface of the front plate may be larger than the area of the main surface of the reflective layer, may be the same, or may be smaller. A reflective layer may be adhered to a part of the main surface of the front plate, and another type of reflective layer such as a metal foil may be adhered or formed to other parts. With such a configuration, it is possible to display an image on a part of the mirror. On the other hand, the reflective layer may be adhered to the entire surface of the main surface of the front plate. Further, in the mirror with an image display function, a half mirror of the main surface having the same area as the image display portion of the image display device may be used, and the mirror has a main surface area larger or smaller than the image display portion of the image display device. A half mirror may be used. By selecting these relationships, the ratio and position of the surface of the image display unit to the entire surface of the mirror can be adjusted.
Further, the half mirror may be a laminated glass, and the intermediate layer of the laminated glass may include an nλ / 4 retardation film, or an nλ / 4 retardation film and a reflective layer.
The film thickness of the half mirror is not particularly limited, but is preferably 100 μm to 20 mm, more preferably 200 μm to 15 mm, and even more preferably 300 μm to 10 mm.

<Nλ / 4 retardation film>
The half mirror includes an nλ / 4 retardation film. The nλ / 4 retardation film is either a λ / 4 retardation film or a (mλ ± λ / 4) retardation film (m is a natural number), and the phase of the reflected light is substantially ± λ / 4 Has a shifting function. From the viewpoint of ease of production and function, n may be 1, 3, 5 or 7. That is, the nλ / 4 retardation film may be a λ / 4 retardation film, a 3λ / 4 retardation film, a 5λ / 4 retardation film, or a 7λ / 4 retardation film. Specifically, the λ / 4 retardation film may be a retardation film having a frontal retardation of 138 nm ± 10 nm, preferably 138 nm ± 5 nm at a wavelength of 550 nm, and the 3λ / 4 retardation film has a wavelength of 550 nm. A retardation film having a frontal retardation of 413 nm ± 10 nm, preferably 413 nm ± 5 nm may be used, and a 5λ / 4 retardation film has a frontal retardation of 688 nm ± 10 nm, preferably 688 nm ± 5 nm at a wavelength of 550 nm. It may be a retardation film, and the 7λ / 4 retardation film may be a retardation film having a front retardation of 963 nm ± 10 nm, preferably 963 nm ± 5 nm at a wavelength of 550 nm. The nλ / 4 retardation film is preferably a λ / 4 retardation film, a 3λ / 4 retardation film, or a 5λ / 4 retardation film, and is a λ / 4 retardation film or a 3λ / 4 retardation film. This is more preferable, and a λ / 4 retardation film is most preferable.

In the present specification, the "nλ / 4 retardation film" and the "1/4 wave plate" described later are used separately from the viewpoint of the arrangement position and the purpose of use, but the nλ / 4 retardation film is at the λ / 4 position. When it is a retardation film, the "nλ / 4 retardation film" and the "1/4 wave plate" may be the same.

It is known that tempered glass used for vehicle window glass, particularly rear glass (for example, tempered glass not composed of laminated glass) has a birefringent distribution. Tempered glass is generally produced by heating float plate glass to 700 ° C. near the softening point and then blowing air onto the glass surface to quench it. By this treatment, the temperature of the glass surface drops first and shrinks and hardens, while the temperature inside the glass drops later than the surface and shrinks later, so a stress distribution occurs inside and there is no birefringence. Birefringence distribution occurs in the tempered glass even when the float plate glass is used.

Therefore, it is considered that the above-mentioned unevenness occurs in the mirror reflected image due to the light incident on the front surface of the mirror with the image display function, in particular, passing through the rear glass of the vehicle in which the tempered glass produced as described above is used. That is, the polarized light component of sunlight is biased to either p-polarized light or s-polarized light depending on the positional relationship between the sun and the observer. In addition, the proportion of s-polarized light is high in the light reflected on the surface of water, asphalt, glass, or the like. Such polarized light exists in the natural world, and when light containing polarized light passes through the rear glass, a polarized light distribution is generated in the transmitted light due to the biased distribution of birefringence of the rear glass. When these lights are reflected by the linearly polarized light reflecting layer or the circularly polarized light reflecting layer of the vehicle mirror, the reflectance differs depending on the difference in the polarization state of the incident light, and uneven brightness is visually recognized. In the mirror with an image display function of the present invention, by using an nλ / 4 retardation film having a phase difference of a predetermined size, it is difficult for a difference in the intensity of reflected light to occur between the phases of incident light having different polarization states depending on the location. It is presumed that it became possible to reduce unevenness by shifting to the area.

In the present specification, p-polarized light means polarized light that oscillates in a direction parallel to the incident surface of light, and s-polarized light means polarized light that oscillates in a direction perpendicular to the incident surface of light. The incident surface means a surface perpendicular to the reflecting surface (such as the ground) and containing the incident light rays and the reflected rays.

In the mirror with an image display function, the nλ / 4 retardation film may be provided so that the nλ / 4 retardation film, the reflection layer, and the image display device are provided in this order. When the half mirror has a front plate, the front plate, the nλ / 4 retardation film, the reflective layer, and the image display device may be in this order. The front plate may also serve as an nλ / 4 retardation film.

As the nλ / 4 retardation film, the same one as the 1/4 wave plate described later can be used, and by adjusting the film thickness etc. using the same material, the 3/4λ retardation film, 5 / A 4λ retardation film or a 7 / 4λ retardation film can be formed and used. The nλ / 4 retardation film is particularly preferably formed by arranging and fixing a polymerizable liquid crystal compound or a polymer liquid crystal compound.

By providing the nλ / 4 retardation film on the rear glass of the vehicle, it is possible to eliminate the unevenness of the mirror reflection image described above. At this time, the mirror with an image display function does not have to include the nλ / 4 retardation film.

<Reflective layer>
As the reflective layer, a reflective layer that can function as a transflective semi-reflective layer may be used. That is, the reflective layer functions so that the image is displayed on the front surface of the mirror with the image display function by transmitting the light emitted from the image display device when the image is displayed, while the reflection layer is reflected when the image is not displayed. The layer may be a layer that reflects at least a part of the incident light from the front surface direction, transmits the reflected light from the image display device, and functions so that the front surface of the mirror with an image display function serves as a mirror.
As the reflective layer, a polarized reflective layer is used. The polarized light reflecting layer may be a linearly polarized light reflecting layer or a circularly polarized light reflecting layer.

[Linear polarization reflection layer]
Examples of the linearly polarized light reflecting layer include (i) a linearly polarized light reflecting plate having a multi-layer structure, (ii) a polarizer in which thin films having different double refraction are laminated, (iii) a wire grid type polarizing element, (iv) a polarizing prism, and (v). ) Scattering anisotropic type polarizing plate and the like can be mentioned.

(I) Examples of the linearly polarized light reflector having a multilayer structure include those formed by laminating a plurality of layers of dielectric thin films having different refractive indexes from each other. In order to obtain a wavelength selective reflective film, it is preferable to alternately stack a plurality of layers of a dielectric thin film having a high refractive index and a dielectric thin film having a low refractive index, but the type is not limited to two or more, and more types. It may be. The number of layers is preferably 2 to 20 layers, more preferably 2 to 12 layers, further preferably 4 to 10 layers, and particularly preferably 6 to 8 layers. If the number of layers exceeds 20, the production efficiency may decrease due to the multi-layer deposition, and the object and effect of the present invention may not be achieved.

The stacking order of the dielectric thin films is not particularly limited and may be appropriately selected depending on the intended purpose. For example, when the refractive index of adjacent films is high, a film having a lower refractive index is laminated first. .. On the contrary, when the refractive index of the adjacent layer is low, a film having a higher refractive index is laminated first. The boundary between high and low refractive index is 1.8. It should be noted that whether the refractive index is high or low is not absolute, and among the materials having a high refractive index, those having a relatively large refractive index and those having a relatively small refractive index may exist, and these are used alternately. You may.

Examples of the material of the dielectric thin film having a high refractive index include Sb ₂ O ₃ , Sb ₂ S ₃ , Bi ₂ O ₃ , CeO ₂ , CeF ₃ , HfO ₂ , La ₂ O ₃ , Nd ₂ O ₃ , Pr _6. Examples thereof include O ₁₁ , Sc ₂ O ₃ , SiO, Ta ₂ O ₅ , TiO ₂ , TlCl, Y ₂ O ₃ , ZnSe, ZnS, and ZrO ₂ . Among these, Bi ₂ O ₃ , CeO ₂ , CeF ₃ , HfO ₂ , SiO, Ta ₂ O ₅ , TiO ₂ , Y ₂ O ₃ , ZnSe, ZnS, ZrO ₂ are preferable, and among these, SiO, Ta ₂ O ₅ , TiO ₂ , Y ₂ O ₃ , ZnSe, ZnS, and ZrO ₂ are particularly preferable.

Materials for the low refractive index dielectric thin film include, for example, Al ₂ O ₃ , BiF ₃ , CaF ₂ , LaF ₃ , PbCl ₂ , PbF ₂ , LiF, MgF ₂ , MgO, NdF ₃ , SiO ₂ , Si ₂ O. ₃ , NaF, ThO ₂ , ThF ₄ , and the like. Among these, Al ₂ O ₃ , BiF ₃ , CaF ₂ , MgF ₂ , MgO, SiO ₂ , Si ₂ O ₃ are preferable, and Al ₂ O ₃ , CaF ₂ , MgF ₂ , MgO, SiO ₂ , Si ₂ O ₃ Is particularly preferable.
In the material of the dielectric thin film, the atomic ratio is not particularly limited and can be appropriately selected depending on the intended purpose, and the atomic ratio can be adjusted by changing the atmospheric gas concentration at the time of film formation.

The method for forming the dielectric thin film is not particularly limited and may be appropriately selected depending on the intended purpose. For example, an ion plating method, a vacuum deposition method such as an ion beam, or a physical vapor deposition method such as sputtering (sputtering or the like). PVD method), chemical vapor deposition method (CVD method), and the like. Among these, the vacuum deposition method and the sputtering method are preferable, and the sputtering method is particularly preferable.
As the sputtering method, a DC sputtering method having a high film formation rate is preferable. In the DC sputtering method, it is preferable to use a material having high conductivity.
Further, as a method of forming a multi-layer film by a sputtering method, for example, (1) a one-chamber method in which a plurality of targets are alternately or sequentially formed in one chamber, and (2) a film is continuously formed in a plurality of chambers. There is a multi-chamber method. Among these, the multi-chamber method is particularly preferable from the viewpoint of productivity and prevention of material contamination.
The film thickness of the dielectric thin film is preferably λ / 16 to λ, more preferably λ / 8 to 3λ / 4, and more preferably λ / 6 to 3λ / 8, on the order of optical wavelength.

The light propagating in the dielectric vapor deposition layer is determined by the product of the thickness of the dielectric thin film and the refractive index of the film with respect to the light due to the multiple reflection of a part of the light for each dielectric thin film and the interference of the reflected light. Only light of the wavelength is selectively transmitted. Further, the central transmission wavelength of the dielectric thin-film deposition layer has an angle dependence on the incident light, and the transmitted wavelength can be changed by changing the incident light.

(Ii) As the polarizer in which thin films having different birefringences are laminated, for example, those described in Japanese Patent Publication No. 9-506837 can be used. Specifically, when processed under the conditions selected to obtain the refractive index relationship, a polarizer can be formed using a wide variety of materials. In general, one of the first materials needs to have a different refractive index than the second material in the chosen direction. This difference in refractive index can be achieved by a variety of methods, including stretching, extrusion, or coating during or after film formation. Further, it is preferable to have similar rheological properties (eg, melt viscosity) so that the two materials can be extruded at the same time.
A commercially available product can be used as the polarizer in which thin films having different birefringences are laminated, and examples of the commercially available product include DBEF (registered trademark) (manufactured by 3M).

(Iii) The wire grid type polarizer is a polarizer that transmits one of polarized light and reflects the other by birefringence of a thin metal wire.
The wire grid polarizer is a periodic array of metal wires, and is mainly used as a polarizer in the terahertz wave band. In order for the wire grid to function as a polarizer, the wire spacing must be sufficiently smaller than the wavelength of the incident electromagnetic wave.
In the wire grid polarizer, metal wires are arranged at equal intervals. The polarization component in the polarization direction parallel to the longitudinal direction of the metal wire is reflected by the wire grid polarizer, and the polarization component in the vertical polarization direction is transmitted through the wire grid polarizer.

As the wire grid type polarizing element, a commercially available product can be used, and examples of the commercially available product include a wire grid polarizing filter 50 × 50 and NT46-636 manufactured by Edmond Optics.

By using the linearly polarized light reflecting layer, in combination with the nλ / 4 retardation film, the incident light from the front side can be reflected as circularly polarized light, and the incident light from the image display device can be transmitted as circularly polarized light. Therefore, in the mirror with an image display function using the linearly polarized light reflecting layer, the displayed image and the mirror reflected image can be observed even through polarized sunglasses without depending on the direction of the mirror with the image display function.

[Circular polarized reflection layer]
As the circularly polarized light reflecting layer, it is preferable to use a circularly polarized light reflecting layer including a cholesteric liquid crystal layer (hereinafter, may be referred to as “cholesteric circularly polarized light reflecting layer”).

(Cholesteric liquid crystal layer)
The cholesteric circularly polarized light reflecting layer includes at least one cholesteric liquid crystal layer. The cholesteric liquid crystal layer included in the cholesteric circularly polarized light reflecting layer may be any one that exhibits selective reflection in the visible light region.
The circularly polarized light reflecting layer may include two or more cholesteric liquid crystal layers, and may include other layers such as an alignment layer. The circularly polarized light reflecting layer preferably consists of only a cholesteric liquid crystal layer. When the circularly polarized light reflecting layer includes a plurality of cholesteric liquid crystal layers, it is preferable that they are in direct contact with the adjacent cholesteric liquid crystal layers. The circularly polarized light reflecting layer preferably includes three or more cholesteric liquid crystal layers such as three layers and four layers.
The film thickness of the cholesteric circularly polarized light reflecting layer is preferably in the range of 2.0 μm to 300 μm, more preferably in the range of 8.0 to 200 μm.

In the present specification, the cholesteric liquid crystal layer means a layer in which the cholesteric liquid crystal phase is fixed. The cholesteric liquid crystal layer may be simply referred to as a liquid crystal layer.
The cholesteric liquid crystal phase selectively reflects circularly polarized light of either right-handed or left-handed circularly polarized light in a specific wavelength range, and selectively transmits circularly polarized light of the other sense. It is known to show. In the present specification, the circular polarization selective reflection may be simply referred to as a selective reflection.

As a film containing a layer in which a cholesteric liquid crystal phase exhibiting circular polarization selective reflectivity is fixed, many films formed from a composition containing a polymerizable liquid crystal compound have been known conventionally, and the cholesteric liquid crystal layer has been conventionally known. You can refer to the technology.

The cholesteric liquid crystal layer may be a layer in which the orientation of the liquid crystal compound which is the cholesteric liquid crystal phase is maintained, and typically, the polymerizable liquid crystal compound is placed in the orientation state of the cholesteric liquid crystal phase and then irradiated with ultraviolet rays. The layer may be polymerized and cured by heating or the like to form a non-fluid layer, and at the same time, the layer may be changed to a state in which the orientation form is not changed by an external field or an external force. In the cholesteric liquid crystal layer, it is sufficient that the optical properties of the cholesteric liquid crystal phase are retained in the layer, and the liquid crystal compound in the layer does not have to exhibit liquid crystal property anymore. For example, the polymerizable liquid crystal compound may have a high molecular weight due to a curing reaction and no longer have liquid crystal properties.

The central wavelength λ of the selective reflection of the cholesteric liquid crystal layer depends on the pitch P (= spiral period) of the spiral structure in the cholesteric phase, and follows the relationship between the average refractive index n and λ = n × P of the cholesteric liquid crystal layer. The selective reflection center wavelength and full width at half maximum of the cholesteric liquid crystal layer can be obtained as follows.
When the transmission spectrum of the light reflecting layer (measured from the normal direction of the cholesteric liquid crystal layer) is measured using a spectrophotometer UV3150 (Shimadzu Seisakusho), a decrease peak of the transmittance is observed in the selective reflection region. Of the two wavelengths having a transmittance of 1/2 of the maximum peak height, assuming that the wavelength value on the short wave side is λ1 (nm) and the wavelength value on the long wave side is λ2 (nm). The center wavelength and full width at half maximum of selective reflection can be expressed by the following equations.
Selective reflection center wavelength = (λ1 + λ2) / 2
Half width = (λ2-λ1)
The central wavelength λ of the selective reflection of the cholesteric liquid crystal layer, which is obtained as described above, usually coincides with the wavelength at the center of gravity of the reflection peak of the circular polarization reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer. In the present specification, the central wavelength of selective reflection means the central wavelength when measured from the normal direction of the cholesteric liquid crystal layer.

As can be seen from the above equation of λ = n × P, the center wavelength of selective reflection can be adjusted by adjusting the pitch of the spiral structure. The central wavelength λ can be adjusted in order to selectively reflect either right-handed or left-handed circularly polarized light with respect to light of a desired wavelength by adjusting the n-value and P-value.

When light is obliquely incident on the cholesteric liquid crystal layer, the center wavelength of selective reflection shifts to the short wavelength side. Therefore, it is preferable to adjust n × P so that λ calculated according to the above equation of λ = n × P has a long wavelength with respect to the wavelength of selective reflection required for image display. Let λ _{d be} the center wavelength of selective reflection when light rays pass at an angle of θ ₂ with respect to the normal direction of the cholesteric liquid crystal layer (the spiral axis direction of the cholesteric liquid crystal layer) in the cholesteric liquid crystal layer having a refractive index of n _2. Then, λ _d is expressed by the following equation.
λ _d = n ₂ × P × cos θ ₂

In consideration of the above, by designing the center wavelength of the selective reflection of the cholesteric liquid crystal layer included in the circularly polarized light reflecting layer, it is possible to prevent a decrease in visibility of the image from an oblique direction. It is also possible to intentionally reduce the visibility of the image from an angle. This is useful, for example, in smartphones and personal computers because it can prevent peeping. Further, due to the above-mentioned property of selective reflection, the mirror with an image display function of the present invention may give color to the image and the mirror reflection image when viewed from an oblique direction. It is also possible to prevent such a tint by including a cholesteric liquid crystal layer having a central wavelength of selective reflection in the infrared light region in the circularly polarized light reflecting layer. Specifically, the center wavelength of the selective reflection in the infrared light region in this case may be 780 to 900 nm, preferably 780 to 850 nm.
When the cholesteric liquid crystal layer having the central wavelength of selective reflection is provided in the infrared light region, it is preferable that the cholesteric liquid crystal layer having the central wavelength of selective reflection in the visible light region is located closest to the image display device.

Since the pitch of the cholesteric liquid crystal phase depends on the type of chiral auxiliary used together with the polymerizable liquid crystal compound or the concentration thereof added, a desired pitch can be obtained by adjusting these. For the measurement method of spiral sense and pitch, use the method described in "Introduction to Liquid Crystal Chemistry Experiment", edited by Liquid Crystal Society of Japan, Sigma Publishing, 2007, p. 46, and "Liquid Crystal Handbook", Liquid Crystal Handbook Editorial Committee, Maruzen, p. 196. be able to.

In the mirror with an image display function of the present invention, the circularly polarized light reflection layer has a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of red light and a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of green light. And a cholesteric liquid crystal layer having a central wavelength of selective reflection in the wavelength range of blue light are preferably included. The reflective layer is, for example, a cholesteric liquid crystal layer having a central wavelength of selective reflection at 400 nm to 500 nm, a cholesteric liquid crystal layer having a central wavelength of selective reflection at 500 nm to 580 nm, and a cholesteric liquid crystal having a central wavelength of selective reflection at 580 nm to 700 nm. It is preferable to include a layer.

Further, when the circularly polarized light reflecting layer includes a plurality of cholesteric liquid crystal layers, it is preferable that the cholesteric liquid crystal layer closer to the image display device has a longer center wavelength of selective reflection. With such a configuration, it is possible to suppress the oblique color tint in the image.

In particular, in a mirror with an image display function using a cholesteric circular polarization reflection layer that does not include a 1/4 wave plate, the center wavelength of selective reflection of each cholesteric liquid crystal layer is 5 nm or more with the wavelength of the emission peak of the image display device. It is preferable to make them different. This difference is more preferably 10 nm or more. By shifting the center wavelength of the selective reflection and the wavelength of the emission peak for displaying the image of the image display device, the light for displaying the image is not reflected by the cholesteric liquid crystal layer, and the displayed image can be brightened. The wavelength of the emission peak of the image display device can be confirmed by the emission spectrum of the image display device when it is displayed in white. The peak wavelength may be any peak wavelength in the visible light region of the emission spectrum. For example, the emission peak wavelength λR of the red light, the emission peak wavelength λG of the green light, and the emission peak wavelength λB of the blue light of the image display device. It may be any one or more selected from the group consisting of. The central wavelength of selective reflection of the cholesteric liquid crystal layer is 5 nm or more, preferably 5 nm or more, for all of the above-mentioned red light emission peak wavelength λR, green light emission peak wavelength λG, and blue light emission peak wavelength λB of the image display device. It is preferable that the difference is 10 nm or more. When the circularly polarized light reflecting layer includes a plurality of cholesteric liquid crystal layers, the center wavelength of the selective reflection of all the cholesteric liquid crystal layers is set to be different from the peak wavelength of the light emitted by the image display device by 5 nm or more, preferably 10 nm or more. do it. For example, when the image display device is a full-color display device that shows the emission peak wavelength λR of red light, the emission peak wavelength λG of green light, and the emission peak wavelength λB of blue light in the emission spectrum at the time of white display. The central wavelengths of selective reflection of the cholesteric liquid crystal layer may be different from each of λR, λG, and λB by 5 nm or more, preferably 10 nm or more.

By adjusting the center wavelength of the selective reflection of the cholesteric liquid crystal layer to be used according to the emission wavelength range of the image display device and the usage mode of the circularly polarized light reflecting layer, a bright image can be displayed with high light utilization efficiency. Examples of the usage mode of the circularly polarized light reflecting layer include the angle of incidence of light on the circularly polarized light reflecting layer, the image observation direction, and the like.

As each cholesteric liquid crystal layer, a cholesteric liquid crystal layer having a spiral sense of either right or left is used. The sense of reflected circular polarization of the cholesteric liquid crystal layer matches the sense of spiral. The spiral senses of the plurality of cholesteric liquid crystal layers may all be the same or may contain different ones. That is, it may include a cholesteric liquid crystal layer having either the right or left sense, or may include a cholesteric liquid crystal layer having both right and left senses. However, in a mirror with an image display function including a quarter wave plate, it is preferable that the spiral senses of the plurality of cholesteric liquid crystal layers are all the same. The sense of the spiral at that time may be determined according to the sense of circularly polarized light of the sense obtained by emitting from the image display device and passing through the 1/4 wave plate as each cholesteric liquid crystal layer. Specifically, a cholesteric liquid crystal layer having a spiral sense that transmits circularly polarized light of the sense obtained by emitting from an image display device and transmitting through a quarter wave plate may be used.

The full width at half maximum Δλ (nm) of the selective reflection band indicating selective reflection depends on the birefringence Δn of the liquid crystal compound and the pitch P, and follows the relationship of Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by adjusting the type of the polymerizable liquid crystal compound and its mixing ratio, or by controlling the temperature at the time of fixing the orientation.
In order to form one kind of cholesteric liquid crystal layer having the same central wavelength of selective reflection, a plurality of cholesteric liquid crystal layers having the same period P and the same spiral sense may be laminated. By stacking cholesteric liquid crystal layers having the same period P and the same spiral sense, the circular polarization selectivity can be increased at a specific wavelength.

(1/4 wave plate)
A mirror with an image display function using a cholesteric circularly polarized light reflecting layer may further include a quarter wave plate.
By including a 1/4 wave plate between the image display device and the cholesteric circularly polarized light reflecting layer, in particular, the light from the image display device displaying the image by linear polarization is converted into circularly polarized light and cholesteric circularly polarized light. It is possible to make it incident on the reflective layer. Therefore, the amount of light reflected by the circularly polarized light reflecting layer and returned to the image display device side can be significantly reduced, and a bright image can be displayed. Further, by using the 1/4 wave plate, it is possible to configure the cholesteric circularly polarized light reflecting layer so as not to generate the circularly polarized light of the sense reflected on the image display device side, so that the image due to multiple reflection between the image display device and the half mirror can be obtained. Display quality is unlikely to deteriorate.
That is, for example, the center wavelength of the selective reflection of the cholesteric liquid crystal layer included in the cholesteric circular polarization reflecting layer is substantially the same as the emission peak wavelength of blue light in the emission spectrum when white is displayed on the image display device (for example, the difference is less than 5 nm). Even if this is the case, the emitted light of the image display device can be transmitted to the front side without causing the circular polarization of the sense reflected on the image display side in the circular polarization reflecting layer.

It is preferable that the 1/4 wave plate used in combination with the cholesteric circularly polarized light reflecting layer is angle-adjusted so that the image becomes brightest when it is adhered to an image display device. That is, the relationship between the polarization direction (transmission axis) of the linearly polarized light and the slow axis of the 1/4 wave plate so as to transmit the linearly polarized light best to the image display device displaying the image by linearly polarized light. Is preferably adjusted. For example, in the case of a single-layer 1/4 wave plate, it is preferable that the transmission axis and the slow phase axis form an angle of 45 °. The light emitted from the image display device displaying the image by linearly polarized light is circularly polarized with either the right or left sense after passing through the 1/4 wave plate. The circularly polarized light reflecting layer may be composed of a cholesteric liquid crystal layer having a twisting direction that transmits the circularly polarized light of the above sense.

The 1/4 wave plate may be a retardation layer that functions as a 1/4 wave plate in the visible light region. Examples of the 1/4 wave plate include a single-layer 1/4 wave plate, a wideband 1/4 wave plate in which a 1/4 wave plate and a 1/2 wavelength retardation plate are laminated, and the like.
The front phase difference of the former 1/4 wave plate may be 1/4 of the emission wavelength of the image display device. Therefore, for example, when the emission wavelength of the image display device is 450 nm, 530 nm, or 640 nm, the wavelength of 450 nm is 112.5 nm ± 10 nm, preferably 112.5 nm ± 5 nm, more preferably 112.5 nm, and 132 at the wavelength of 530 nm. Reverse dispersibility such that the phase difference is 160 nm ± 10 nm, preferably 160 nm ± 5 nm, more preferably 160 nm at wavelengths of .5 nm ± 10 nm, preferably 132.5 nm ± 5 nm, more preferably 132.5 nm, 640 nm. The retardation layer is most preferable as the 1/4 wave plate, but a retardation plate having a small wavelength dispersibility of the retardation and a retardation plate having a forward dispersibility can also be used. The inverse dispersibility means the property that the absolute value of the phase difference increases as the wavelength becomes longer, and the forward dispersibility means the property that the absolute value of the phase difference increases as the wavelength becomes shorter.

In the laminated 1/4 wave plate, the 1/4 wave plate and the 1/2 wavelength retardation plate are bonded together at an angle of 60 ° on the slow axis thereof, and the 1/2 wavelength retardation plate side is linearly polarized. It is placed on the incident side and the slow axis of the 1/2 wavelength retardation plate is used crossing the polarization plane of the incident linearly polarized light at 15 ° or 75 °, and the inverse dispersibility of the phase difference. Can be suitably used because of its good condition.

The λ / 4 wave plate is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a quartz plate, a stretched polycarbonate film, a stretched norbornene-based polymer film, a transparent film oriented containing inorganic particles having birefringence such as strontium carbonate, and an inorganic dielectric deposited obliquely on a support. Examples include thin films.

Examples of the λ / 4 wavelength plate include the double-refractive film having a large retardation and the double refraction having a small retardation described in (1) JP-A-5-27118 and JP-A-5-27119. A retardation plate in which sex films are laminated so that their optical axes are orthogonal to each other, and (2) a polymer film having a λ / 4 wavelength at a specific wavelength described in JP-A-10-68816. , A retardation plate that can obtain λ / 4 wavelength in a wide wavelength range by laminating a polymer film made of the same material and having λ / 2 wavelength at the same wavelength, (2) JP-A-10-90521. (3) A retardation plate capable of achieving a λ / 4 wavelength in a wide wavelength region by laminating two polymer films described in (3) The modified polycarbonate film described in International Publication No. 00/26705 pamphlet is used. Phase difference plate capable of achieving λ / 4 wavelength in a wide wavelength region, (4) Phase difference capable of achieving λ / 4 wavelength in a wide wavelength region using the cellulose acetate film described in International Publication No. 00/65384. Boards, etc.
As the λ / 4 wave plate, a commercially available product can be used, and examples of the commercially available product include Pure Ace (registered trademark) WR (polycarbonate film manufactured by Teijin Limited).

The quarter wave plate may be formed by arranging and fixing a polymerizable liquid crystal compound and a polymer liquid crystal compound. For example, in a 1/4 wave plate, a liquid crystal composition is applied to the surface of a temporary support, an alignment film, or a front plate, and a polymerizable liquid crystal compound in the liquid crystal composition is formed in a nematic orientation in a liquid crystal state, and then photocrosslinked. It can be fixed and formed by thermal cross-linking. The details of the liquid crystal composition or the production method will be described later. The 1/4 wave plate is oriented by applying a liquid crystal composition to a temporary support, an alignment film, or the surface of a front plate, forming a composition containing a polymer liquid crystal compound in a nematic orientation in a liquid crystal state, and then cooling the composition. It may be a layer obtained by immobilizing.
The λ / 4 wave plate may be adhered to the cholesteric circularly polarized light reflecting layer by an adhesive layer or may be in direct contact with each other, but the latter is preferable.

(Method for producing 1/4 wave plate and nλ / 4 retardation film formed from cholesteric liquid crystal layer and liquid crystal composition)
Hereinafter, a manufacturing material and a manufacturing method for an nλ / 4 retardation film and a 1/4 wave plate formed from a cholesteric liquid crystal layer and a liquid crystal composition will be described.
Examples of the material used for forming the 1/4 wave plate and the nλ / 4 retardation film include a liquid crystal composition containing a polymerizable liquid crystal compound. Examples of the material used for forming the cholesteric liquid crystal layer include a liquid crystal composition containing a chiral agent (optically active compound). If necessary, the liquid crystal composition further mixed with a surfactant, a polymerization initiator, etc. and dissolved in a solvent or the like is used as a temporary support, a support, an alignment film, an nλ / 4 retardation film, and a cholesteric liquid crystal as a lower layer. It can be applied to a layer, a 1/4 wave plate, or the like, and after orientation and aging, it can be immobilized by curing the liquid crystal composition to form a cholesteric liquid crystal layer or a 1/4 wave plate.

-Polymerizable liquid crystal compound-
As the polymerizable liquid crystal compound, a rod-shaped liquid crystal compound may be used.
Examples of the rod-shaped polymerizable liquid crystal compound include a rod-shaped nematic liquid crystal compound. Examples of the rod-shaped nematic liquid crystal compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxans, trans and alkenylcyclohexylbenzonitriles are preferably used. Not only low molecular weight liquid crystal compounds but also high molecular weight liquid crystal compounds can be used.

The polymerizable liquid crystal compound is obtained by introducing a polymerizable group into the liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, and an unsaturated polymerizable group is preferable, and an ethylenically unsaturated polymerizable group is particularly preferable. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups contained in the polymerizable liquid crystal compound is preferably 1 to 6, and more preferably 1 to 3. Examples of polymerizable liquid crystal compounds include Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, 562,648, 5770107, International Publication WO95 / 22586, WO95. / 24455, WO97 / 00600, WO98 / 23580, WO98 / 52905, JP-A 1-2725551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, and JP-A-2001. The compounds described in JP-A-328973 and the like are included. Two or more kinds of polymerizable liquid crystal compounds may be used in combination. When two or more kinds of polymerizable liquid crystal compounds are used in combination, the orientation temperature can be lowered.

The amount of the polymerizable liquid crystal compound added to the liquid crystal composition is preferably 80 to 99.9% by mass, preferably 85 to 99% by mass, based on the solid content mass (mass excluding the solvent) of the liquid crystal composition. It is more preferably 5.5% by mass, and particularly preferably 90 to 99% by mass.

-Chiral agent: optically active compound-
The material used to form the cholesteric liquid crystal layer preferably contains a chiral agent. The chiral agent has the function of inducing the helical structure of the cholesteric liquid crystal phase. Since the chiral compound has a different sense or pitch of the spiral induced by the compound, it may be selected according to the purpose.
The chiral agent is not particularly limited, and is described in a known compound (for example, Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Agent for TN, STN, p. 199, edited by Japan Society for the Promotion of Science 142 Committee, 1989. Description), isosorbide, and isomannide derivatives can be used.

The chiral agent generally contains an asymmetric carbon atom, but an axial asymmetric compound or a surface asymmetric compound that does not contain an asymmetric carbon atom can also be used as the chiral agent. Examples of axially asymmetric or surface asymmetric compounds include binaphthyl, helicene, paracyclophane and derivatives thereof. The chiral agent may have a polymerizable group. When both the chiral agent and the liquid crystal compound have a polymerizable group, the repeating unit derived from the polymerizable liquid crystal compound and the repeating unit derived from the chiral agent are derived by the polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. Polymers with repeating units can be formed. In this aspect, the polymerizable group of the polymerizable chiral agent is preferably a group of the same type as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and preferably an ethylenically unsaturated polymerizable group. Especially preferable.
Moreover, the chiral agent may be a liquid crystal compound.
The content of the chiral agent in the liquid crystal composition is preferably 0.01 mol% to 200 mol%, more preferably 1 mol% to 30 mol% of the amount of the polymerizable liquid crystal compound.

-Polymer initiator-
The liquid crystal composition preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is allowed to proceed by irradiation with ultraviolet rays, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by irradiation with ultraviolet rays. Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. Nos. 2,376,661 and 236,670), acidoin ethers (described in US Pat. No. 2,448,828), and α-hydrogen-substituted fragrances. Group acidoine compounds (described in US Pat. No. 2722512), polynuclear quinone compounds (described in US Pat. Nos. 3,043127 and 2951758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US Pat. 35493667 (described in US Pat. No. 3,549,67), aclysine and phenazine compounds (Japanese Patent Laid-Open No. 60-105667, US Pat. No. 4,239,850), oxadiazole compounds (described in US Pat. No. 421,970), and the like. ..
The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, preferably 0.5% by mass to 5% by mass, based on the content of the polymerizable liquid crystal compound. More preferred.

-Crosslinking agent-
The liquid crystal composition may optionally contain a cross-linking agent in order to improve the film strength and durability after curing. As the cross-linking agent, one that cures with ultraviolet rays, heat, humidity or the like can be preferably used.
The cross-linking agent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a polyfunctional acrylate compound such as trimethylolpropane tri (meth) acrylate or pentaerythritol tri (meth) acrylate; glycidyl (meth) acrylate. , Epoxy compounds such as ethylene glycol diglycidyl ether; 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) propionate], azilysin compounds such as 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane; hexa Isocyanate compounds such as methylenediisocyanate and biuret-type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; alkoxysilane compounds such as vinyltrimethoxysilane and N- (2-aminoethyl) 3-aminopropyltrimethoxysilane. Be done. Further, a known catalyst can be used depending on the reactivity of the cross-linking agent, and the productivity can be improved in addition to the improvement of the film strength and durability. These may be used alone or in combination of two or more.
The content of the cross-linking agent is preferably 3% by mass to 20% by mass, more preferably 5% by mass to 15% by mass. When the content of the cross-linking agent is 3% by mass or more, the effect of improving the cross-linking density can be obtained. Further, by setting the content to 20% by mass or less, the stability of the formed layer can be maintained.

-Orientation control agent-
An orientation control agent that contributes to stable or rapid planar orientation may be added to the liquid crystal composition. Examples of the orientation control agent include the fluorine (meth) acrylate-based polymers described in paragraphs [0018] to [0043] of JP-A-2007-272185, and paragraphs [0031] to [0034] of JP-A-2012-203237. ] And the like, and examples thereof include compounds represented by the formulas (I) to (IV) described in.
As the orientation control agent, one type may be used alone, or two or more types may be used in combination.

The amount of the orientation control agent added to the liquid crystal composition is preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass, and 0, based on the total mass of the polymerizable liquid crystal compound. 0.02% by mass to 1% by mass is particularly preferable.

-Other additives-
In addition, the liquid crystal composition may contain at least one selected from various additives such as a surfactant for adjusting the surface tension of the coating film and making the film thickness uniform, and a polymerizable monomer. .. Further, if necessary, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a coloring material, metal oxide fine particles, etc. are added to the liquid crystal composition as long as the optical performance is not deteriorated. Can be added.

− Solvent −
The solvent used for preparing the liquid crystal composition is not particularly limited and may be appropriately selected depending on the intended purpose, but an organic solvent is preferably used.
The organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, ethers, etc. Can be mentioned. These may be used alone or in combination of two or more. Among these, ketones are particularly preferable in consideration of the burden on the environment.

-Coating, orientation, polymerization-
The method for applying the liquid crystal composition to the temporary support, the alignment film, the nλ / 4 retardation film, the 1/4 wave plate, the cholesteric liquid crystal layer as the lower layer, etc. is not particularly limited and may be appropriately selected according to the purpose. For example, wire bar coating method, curtain coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method, spin coating method, dip coating method, spray coating method, slide coating method, etc. Be done. It can also be carried out by transferring the liquid crystal composition separately coated on the support. The liquid crystal molecules are oriented by heating the applied liquid crystal composition. Cholesteric orientation may be used when forming the cholesteric liquid crystal layer, and nematic orientation is preferable when forming the nλ / 4 retardation film and 1/4 wave plate. At the time of cholesteric orientation, the heating temperature is preferably 200 ° C. or lower, more preferably 130 ° C. or lower. By this alignment treatment, an optical thin film in which the polymerizable liquid crystal compound is twist-oriented so as to have a spiral axis in a direction substantially perpendicular to the film surface can be obtained. At the time of nematic orientation, the heating temperature is preferably 50 ° C. to 120 ° C., more preferably 60 ° C. to 100 ° C.

The oriented liquid crystal compound can be further polymerized to cure the liquid crystal composition. The polymerization may be either thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferable. It is preferable to use ultraviolet rays for light irradiation. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , 100mJ / cm 2 ~1,500mJ / cm 2 is more preferable. In order to promote the photopolymerization reaction, light irradiation may be carried out under heating conditions or a nitrogen atmosphere. The irradiation ultraviolet wavelength is preferably 350 nm to 430 nm. From the viewpoint of stability, the polymerization reaction rate is preferably high, preferably 70% or more, and more preferably 80% or more. The polymerization reaction rate can be determined by measuring the consumption ratio of the polymerizable functional group using an IR absorption spectrum.

The thickness of each cholesteric liquid crystal layer is not particularly limited as long as it exhibits the above characteristics, but is preferably 1.0 μm or more and 150 μm or less, more preferably 4.0 μm or more and 100 μm or less. Good. The thickness of the 1/4 wave plate formed from the liquid crystal composition is not particularly limited, but may be preferably 0.2 to 10 μm, more preferably 0.5 to 2 μm.

-Temporary support, support, orientation layer-
The liquid crystal composition may be applied to the surface of the temporary support or the alignment layer formed on the surface of the temporary support to form a layer. The temporary support or the temporary support and the alignment layer may be peeled off after the layer is formed.
Further, a support may be used particularly when forming an nλ / 4 retardation film. The support does not have to be peeled off after layer formation. Examples of the temporary support and the support include polyester such as polyethylene terephthalate (PET), polycarbonate, acrylic resin, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, silicone, glass plate and the like. The temporary support may be, for example, one in which the circularly polarized light reflecting layer is adhered to the nλ / 4 retardation film or the support and then peeled off. The temporary support may function as a protective film after the circularly polarized light reflecting layer is adhered to the nλ / 4 retardation film or the support until the circularly polarized light reflecting layer is further adhered to the image display device.

The oriented layer has a rubbing treatment of an organic compound such as a polymer (resin such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, polyamide, modified polyamide), oblique deposition of an inorganic compound, and microgrooves. It can be provided by means such as layer formation or accumulation of organic compounds (eg, ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearylate) by the Langmuir-Brojet method (LB membrane). Further, an orientation layer in which an orientation function is generated by applying an electric field, applying a magnetic field, or irradiating light may be used.
In particular, it is preferable that the alignment layer made of a polymer is subjected to a rubbing treatment and then the liquid crystal composition is applied to the rubbing treated surface. The rubbing treatment can be carried out by rubbing the surface of the polymer layer with paper or cloth in a certain direction.
The liquid crystal composition may be applied to the surface of the temporary support without providing the alignment layer, or the surface of the temporary support that has been rubbed.
The thickness of the alignment layer is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm.

-Laminated film of layers formed from polymerizable liquid crystal compounds-
When forming a laminated film composed of a plurality of cholesteric liquid crystal layers and a laminated film composed of a 1/4 wave plate and a plurality of cholesteric liquid crystal layers, they are directly on the surface of the 1/4 wave plate or the previous cholesteric liquid crystal layer, respectively. , A liquid crystal composition containing a polymerizable liquid crystal compound or the like may be applied, and the steps of orientation and fixing may be repeated, and a separately prepared 1/4 wave plate, cholesteric liquid crystal layer, or a laminate thereof may be used with an adhesive or the like. Although they may be laminated, the former is preferable. When an adhesive layer usually provided with a film thickness of 0.5 to 10 μm is used, interference unevenness due to uneven thickness of the adhesive layer may be observed. Therefore, it is preferable to laminate without using the adhesive layer. Is. Further, in the laminated film of the cholesteric liquid crystal layer, the next cholesteric liquid crystal layer is formed so as to be in direct contact with the surface of the previously formed cholesteric liquid crystal layer, so that the liquid crystal on the air interface side of the previously formed cholesteric liquid crystal layer is formed. This is because the orientation of the molecules and the orientation of the liquid crystal molecules on the lower side of the cholesteric liquid crystal layer formed on the molecules match, and the polarization characteristics of the laminated body of the cholesteric liquid crystal layer are improved.
Further, the nλ / 4 retardation film may also form a reflective layer and a laminated film, and at the time of formation, a liquid crystal composition containing a polymerizable liquid crystal compound or the like is directly applied to the surface of the nλ / 4 retardation film. Then, the steps of orientation and fixing may be repeated, or the nλ / 4 retardation film, a reflective layer, an adhesive or the like prepared separately may be used for laminating.

<Front plate>
The mirror with an image display function of the present invention may have a front plate.
The front plate may be flat or curved.
The front plate may be in direct contact with the nλ / 4 retardation film, or may be directly adhered by an adhesive layer or the like. It is preferable that they are directly adhered by an adhesive layer or the like.
The front plate is not particularly limited. As the front plate, a glass plate or a plastic film used for manufacturing a normal mirror can be used. The front plate is preferably transparent in the visible light region. Here, "transparent" in the visible light region means that the light transmittance in the visible light region is 80% or more, preferably 85% or more. The light transmittance used as a measure of transparency is the light transmittance obtained by the method described in JIS-K7105. The light transmittance is the light transmittance obtained by the method described in JIS A5759. That is, the transmittance of each wavelength from 380 nm to 780 nm is measured with a spectrophotometer, and multiplied by the spectral distribution of CIE daylight D65, the wavelength distribution of CIE light adaptation standard luminosity, and the weighting coefficient obtained from the wavelength interval. The visible light transmittance is obtained by weighted averaging.

Further, the front plate preferably has a small birefringence. For example, the front phase difference may be 20 nm or less, preferably less than 10 nm, and more preferably 5 nm or less. Examples of the above-mentioned plastic film include polyester such as polyethylene terephthalate (PET), polycarbonate, acrylic resin, epoxy resin, polyurethane, polyamide, polyolefin, cellulose derivative, silicone and the like.

The curved front plate can be manufactured by a plastic processing method such as injection molding. In injection molding, for example, a resin product can be obtained by melting raw material plastic pellets with heat, injecting them into a mold, and then cooling and solidifying them.

The film thickness of the front plate may be about 100 μm to 10 mm, preferably 200 μm to 5 mm, more preferably 500 μm to 2 mm, and even more preferably 500 μm to 1000 μm.

The front plate may also serve as an nλ / 4 retardation film. That is, the front plate may be an nλ / 4 retardation film. Specifically, a plastic plate or the like having a phase difference of nλ / 4 may be the front plate, or a laminated glass containing an nλ / 4 retardation film in the intermediate layer may be the front plate.

(Laminated glass containing nλ / 4 retardation film in the intermediate layer)
Laminated glass includes two glass plates and an intermediate layer between them. In general, laminated glass is made by sandwiching an interlayer film sheet for laminated glass between two glass plates, repeating heat treatment and pressure treatment (treatment with a rubber roller, etc.) several times, and finally autoclaving or the like. It can be produced by a method of performing heat treatment under pressurized conditions using the above. The thickness of the glass plate is not particularly limited, but may be about 0.5 mm to 5 mm, preferably 1 mm to 3 mm, and more preferably 2.0 to 2.3 mm.

The laminated glass containing the nλ / 4 retardation film in the intermediate layer may be formed by forming the nλ / 4 retardation film on the surface of the glass plate and then performing a normal laminated glass manufacturing process. At this time, the nλ / 4 retardation film may be bonded to a glass plate with an adhesive, for example.
Further, in the laminated glass containing the nλ / 4 retardation film in the intermediate layer, the laminated interlayer film sheet for laminated glass containing the nλ / 4 retardation film is used as the interlayer film sheet, and the above heat treatment and pressure treatment can be performed. It may be done and formed. The laminated interlayer film sheet for laminated glass containing the nλ / 4 retardation film can be formed by laminating the nλ / 4 retardation film to the surface of a known interlayer film sheet. Alternatively, the nλ / 4 retardation film can be formed by sandwiching it between two known interlayer film sheets. The two interlayer sheets may be the same or different, but are preferably the same.

As the interlayer film sheet, for example, a resin film containing a resin selected from the group of polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer and chlorine-containing resin can be used. The resin is preferably the main component of the interlayer film sheet. The main component means a component that accounts for 50% by mass or more of the interlayer film sheet. Among the above resins, polyvinyl butyral or ethylene-vinyl acetate copolymer is preferable, and polyvinyl butyral is more preferable. The resin is preferably a synthetic resin.
Polyvinyl butyral can be obtained by acetalizing polyvinyl alcohol with butyraldehyde. The preferred lower limit of the degree of acetalization of polyvinyl butyral is 40%, the preferred upper limit is 85%, the more preferred lower limit is 60%, and the more preferred upper limit is 75%.

The polyvinyl butyral can be prepared by acetalizing polyvinyl alcohol with butyraldehyde. Polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate, and polyvinyl alcohol having a saponification degree of 80 to 99.8 mol% is generally used.
The preferable lower limit of the degree of polymerization of the polyvinyl alcohol is 200, and the preferable upper limit is 3000. If it is less than 200, the penetration resistance of the obtained laminated glass may be lowered, and if it exceeds 3000, the moldability of the resin film is deteriorated, and the rigidity of the resin film becomes too large, resulting in poor workability. Sometimes. A more preferred lower limit is 500 and a more preferred upper limit is 2000.

A known bonding method can be used for bonding the nλ / 4 retardation film and the interlayer film sheet, but it is preferable to use a laminating process. When the laminating treatment is carried out, it is preferable to carry out the laminating treatment under some heating and pressurizing conditions so that the nλ / 4 retardation film and the interlayer film sheet do not peel off after processing.
In order to stably perform the lamination, the film surface temperature on the bonding side of the interlayer film sheet is preferably 50 to 130 ° C., more preferably 70 to 100 ° C.
It is preferable to pressurize at the time of laminating. Pressurization condition is preferably less than 2.0kg / cm ² (0.196MPa), more preferably in the range of 0.5~1.8kg / cm ² (0.049~0.176MPa) , 0.5 to 1.5 kg / cm ² (0.049 to 0.147 MPa), more preferably.

<Adhesive layer>
The mirror with an image display function of the present invention includes a reflective layer and an nλ / 4 retardation film, an nλ / 4 retardation film and a front plate, an image display device and a reflective layer, a 1/4 wave plate and a linearly polarized light reflecting plate, and the like. An adhesive layer for bonding each layer may be included. The adhesive layer may be formed from an adhesive.
From the viewpoint of curing method, there are hot melt type, thermosetting type, photocuring type, reaction curing type, and pressure sensitive adhesive type that does not require curing, and the materials are acrylate type, urethane type, urethane acrylate type, and epoxy, respectively. Uses compounds such as system, epoxy acrylate system, polyolefin system, modified olefin system, polypropylene system, ethylene vinyl alcohol system, vinyl chloride system, chloroprene rubber system, cyanoacrylate system, polyamide system, polyimide system, polystyrene system, polyvinyl butyral system. can do. From the viewpoint of workability and productivity, a photocurable type is preferable as the curing method, and from the viewpoint of optical transparency and heat resistance, it is preferable to use an acrylate-based material, a urethane acrylate-based material, an epoxy acrylate-based material, or the like.

<How to make a half mirror>
The half mirror may be manufactured according to the procedure for manufacturing the reflective layer to be used. A half mirror having a front plate may be manufactured by forming an nλ / 4 retardation film and a reflective layer on the front plate, or the separately prepared nλ / 4 retardation film and the reflective layer are adhered to each other. It may be produced by. For example, it may be produced by transferring the cholesteric circularly polarized light reflecting layer or the 1/4 wave plate and the cholesteric circularly polarized light reflecting layer formed on the temporary support to the nλ / 4 retardation film. For example, a cholesteric liquid crystal layer or a laminate of cholesteric liquid crystal layers is formed on a temporary support to form a cholesteric circularly polarized light reflecting layer, and the surface of the circularly polarized light reflecting layer is adhered to an nλ / 4 retardation film, and then. If necessary, the temporary support can be peeled off to obtain a half mirror. Alternatively, a 1/4 wave plate and a cholesteric liquid crystal layer are sequentially formed on the temporary support to form a laminate of the 1/4 wave plate and the cholesteric circularly polarized light reflecting layer, and this cholesteric liquid crystal layer (circularly polarized light reflection) is formed. A half mirror can be obtained by adhering to the nλ / 4 retardation film on the surface of the layer) and then peeling off the temporary support as needed.

A half mirror of a laminated glass having an nλ / 4 retardation film and a reflective layer in the intermediate layer can be manufactured in the same manner as a laminated glass having an nλ / 4 retardation film in the intermediate layer. For example, the nλ / 4 retardation film and the reflective layer may be formed on the surface of the glass plate and then manufactured through a normal laminated glass manufacturing process, or a laminated interlayer film for laminated glass including the nλ / 4 retardation film and the reflective layer. The sheet may be manufactured using the interlayer film sheet. The laminated interlayer film sheet for laminated glass including the nλ / 4 retardation film and the reflective layer can be formed by laminating the nλ / 4 retardation film and the reflective layer to the surface of a known interlayer film sheet. Alternatively, the nλ / 4 retardation film and the reflective layer can be formed by sandwiching them between two known interlayer film sheets. In a laminated glass half mirror, the nλ / 4 retardation film and the reflective layer may be in direct contact with each other or may be adhered via an adhesive layer.

<<< Manufacturing method of mirror with image display function >>>
The mirror with an image display function of the present invention is manufactured by arranging a half mirror so that the reflection layer side of the nλ / 4 retardation film is the surface side of the image display portion of the image display device. When the half mirror has a front plate, the image display device, the reflective layer, the nλ / 4 retardation film, and the front plate are arranged in this order. After that, if necessary, the image display device and the half mirror may be integrated.
The image display device and the half mirror may be integrated by connecting or adhering with an outer frame or a hinge.

Hereinafter, the present invention will be described in more detail with reference to examples. The materials, reagents, amounts of substances and their ratios, operations, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

<Preparation of coating liquid>
(1) The coating liquid 1 was prepared for the λ / 4 wave plate and the retardation plate, and the coating liquid 2, the coating liquid 3 and the coating liquid 4 were prepared for forming the cholesteric liquid crystal layer with the compositions shown in Table 1 below.

Compound 2 was produced by the method described in JP-A-2005-999248.

<Preparation of cholesteric circularly polarized light reflective layer>
(1) The temporary support (280 mm x 85 mm) uses a PET film (Cosmo Shine A4100, thickness: 100 μm) manufactured by Toyobo Co., Ltd., and is rubbed (rayon cloth, pressure: 0.1 kgf (0.98 N), rotation speed. : 1000 rpm, transport speed: 10 m / min, number of times: 1 round trip).
(2) After applying the coating liquid 1 to the rubbed surface of the PET film using a wire bar, dry it and place it on a hot plate at 30 ° C., and place it on a hot plate of Fusion UV Systems Co., Ltd. Electrodeless lamp "D valve" (60 mW / UV irradiation was carried out at cm ² ) for 6 seconds to fix the liquid crystal phase, and a 1/4 wave plate having a film thickness of 0.8 μm was obtained. After applying the coating liquid 2 to the surface of the obtained layer using a wire bar, it is dried and placed on a hot plate at 30 ° C., and the electrodeless lamp "D bulb" (60 mW / cm ²⁾ manufactured by Fusion UV Systems Co., Ltd. ) Was irradiated with UV for 6 seconds to fix the cholesteric liquid crystal phase to obtain a cholesteric liquid crystal layer having a film thickness of 3.5 μm. Further, the same process is repeated using the coating liquid 3 and the coating liquid 4 in this order, and the laminate A of the 1/4 wave plate and the three cholesteric liquid crystal layers (layer of the coating liquid 3: 3.0 μm, coating liquid 4). Layer: 2.7 μm) was obtained. When the transmission spectrum of the laminate A was measured with a spectrophotometer (V-670, manufactured by JASCO Corporation), transmission spectra having reflection peaks at 630 nm, 540 nm, and 450 nm were obtained.

<Manufacturing of reflective linear polarizing plate>
In accordance with the description in JP-A-9-506837, PEN and copolyester (coPEN) of naphthalate 70 / terephthalate 30 were synthesized in a standard polyester resin synthesis kettle using ethylene glycol as a diol. A single-layer film of PEN and coPEN was extruded and then stretched at a draw ratio of 5: 1 at about 150 ° C. It was confirmed that the refractive index of PEN with respect to the orientation axis was about 1.88, the refractive index with respect to the transverse axis was 1.64, and the refractive index of the coPEN film was about 1.64.
Next, the thickness of the alternating layers of PEN and coPEN was formed to the film thickness shown in Table 2 below by simultaneous extrusion using a 50-slot supply block supplied with a standard extrusion die. By repeating the above, Tables 2 (2) to (5) were formed in order, and a total of 250 layers were laminated. Then, the stretched film was thermoset in an air oven at about 230 ° C. for 30 seconds to obtain a laminate B.

<Making a retardation plate>
A PET film manufactured by Toyobo Co., Ltd. (Cosmo Shine A4100, thickness: 100 μm) is used as a temporary support, and rubbing treatment (rayon cloth, pressure: 0.1 kgf (0.98 N), rotation speed: 1000 rpm, transport speed: 10 m / min, number of times: 1 round trip).
After applying the coating solution 1 to the rubbing surface of the PET film using a wire bar, dried placed 30 ° C. on a hot plate, Fusion UV Systems Ltd. electrodeless lamp "D bulb" (60mW / cm ²⁾ UV irradiation was performed for 6 seconds to fix the liquid crystal phase. After adhering to an acrylic plate (thickness: 0.3 mm) using an adhesive sheet (PDS-1) manufactured by Panac Co., Ltd., the temporary support was peeled off to obtain a retardation plate A. The retardation plates B to D were obtained in the same manner except that the film thickness was changed as shown in Table 3 below. The front phase difference of the obtained retardation plate was measured using AxoScan manufactured by Axometrix. The results are shown in Table 3.

<Making a half mirror>
[Example 1]
The liquid crystal surface of the retardation plate A was bonded to a glass plate having a thickness of 1.8 mm using an adhesive sheet (PDS-1) manufactured by Panac Co., Ltd.
Next, an adhesive LCR0631 manufactured by Toagosei Co., Ltd. was applied to the surface of the cholesteric liquid crystal layer of the laminate A with a wire bar, and then bonded to the surface of the acrylic plate of the retardation plate A using a laminator. At this time, the slow axis of the 1/4 wave plate in the laminated body A and the slow axis of the retardation plate A are arranged so as to have an angle of 90 °. Furthermore, the count of the wire bar and the nip roll pressure of the laminator were adjusted, and the thickness of the adhesive layer was adjusted to 2 μm. After that, it was placed on a hot plate at 50 ° C. and adhered by irradiating it with UV for 30 seconds with an electrodeless lamp "D bulb" (60 mW / cm ² ) manufactured by Fusion UV Systems Co., Ltd., and then the PET film was peeled off. A half mirror of Example 1 was obtained.

[Example 2]
A half mirror of Example 2 was obtained in the same procedure as in Example 1 except that the retardation plate C was used instead of the retardation plate A.
[Example 3]
The same procedure as in Example 1 was carried out except that the laminated body B was used instead of the laminated body A and the slow phase axis of the retardation plate A was attached so as to be inclined by 45 ° with respect to the transmission axis of the laminated body B. The half mirror of Example 3 was obtained.
[Example 4]
A half mirror of Example 4 was obtained in the same procedure as in Example 3 except that the retardation plate C was used instead of the retardation plate A.

[Comparative Example 1]
A half mirror of Comparative Example 1 was obtained in the same procedure as in Example 1 except that the retardation plate A was not used.
[Comparative Example 2]
A half mirror of Comparative Example 2 was obtained in the same procedure as in Example 1 except that the retardation plate B was used instead of the retardation plate A.
[Comparative Example 3]
A half mirror of Comparative Example 3 was obtained in the same procedure as in Example 1 except that the retardation plate D was used instead of the retardation plate A.
[Comparative Example 4]
A half mirror of Comparative Example 4 was obtained in the same procedure as in Example 3 except that the retardation plate A was not used.
[Comparative Example 5]
A half mirror of Comparative Example 5 was obtained in the same procedure as in Example 3 except that the retardation plate B was used instead of the retardation plate A.

<Making a mirror with an image display function>
An image display function by adhering the half mirror produced above to the surface of the image display unit of the image display device (iPad (registered trademark) Retina) so that the glass plate, retardation plate, reflective layer, and image display device are in this order. A mirror with was made. At this time, in the examples and comparative examples using the laminated body A, the slow axis of the 1/4 wave plate in the reflective layer is 45 with respect to the transmission axis of the image display device (polarization direction of the light emission of the LCD). Arranged so that the angle is tilted.

<Evaluation method>
The mirror with the image display function prepared above was attached to the position of the inner mirror of the vehicle (model: Honda 2002 Step WGN) so that the glass plate was on the driver's seat side (observer side) most. The image of the mirror with an image display function and the mirror reflection image, which can be confirmed by the observer in the driver's seat when sunlight is incident on the inner mirror from the rear glass of the vehicle, were evaluated according to the following criteria. The results are shown in Table 4.
[image]
A: Bright image without distortion B: Image with distortion or uneven brightness, or overall dark image [Unevenness of mirror reflection image (derived from rear glass birefringence)]
A: Birefringence of oblique light is almost invisible B: Birefringence of oblique light is visible From the results shown in Table 4, mirror reflection in Examples 1 to 4 using the nλ / 4 retardation film It can be seen that the unevenness due to the birefringence of the rear glass of the image is difficult to see.

Claims (10)

It is a mirror with an image display function that is a rearview mirror of a vehicle.
Including half mirror and image display device
The image display device emits linearly polarized light to form an image.
The half mirror includes an nλ / 4 retardation film and a reflective layer.
n is 1, 3, 5 or 7
In the mirror with an image display function, the nλ / 4 retardation film, the reflection layer, and the image display device are arranged in this order.
A mirror with an image display function, wherein the reflective layer is a linearly polarized light reflecting layer or a circularly polarized light reflecting layer. The mirror with an image display function according to claim 1, wherein n is 1 or 3 . The mirror with an image display function according to claim 1 or 2, wherein the reflective layer is a circularly polarized reflective layer. The mirror with an image display function according to claim 3, wherein the circularly polarized light reflecting layer includes a cholesteric liquid crystal layer. The mirror with an image display function according to claim 4, wherein the circularly polarized light reflecting layer includes three or more cholesteric liquid crystal layers. Including 1/4 wave plate,
The mirror with an image display function according to claim 4 or 5, wherein the half mirror includes the nλ / 4 retardation film, the circularly polarized light reflecting layer, and the 1/4 wave plate in this order. The mirror with an image display function according to claim 6, wherein the circularly polarized light reflecting layer and the 1/4 wave plate are in direct contact with each other. The half mirror includes a front plate
The mirror with an image display function according to any one of claims 1 to 7, which includes the front plate, the nλ / 4 retardation film, and the reflective layer in this order. The half mirror includes a front plate
The front plate is a laminated glass including two glass plates and an intermediate layer between the two glass plates.
The mirror with an image display function according to any one of claims 1 to 7, wherein the intermediate layer includes the nλ / 4 retardation film. The half mirror is a laminated glass containing two glass plates and an intermediate layer between the two glass plates.
The mirror with an image display function according to any one of claims 1 to 7, wherein the intermediate layer includes the nλ / 4 retardation film and the reflection layer.